This invention relates to a reciprocating conveyor or feeder characterized by a trough or pan subjected to a differential reciprocating motion having a quick backward and a relatively slower forward stroke. The quick backward stroke causes the trough to slide under the material while the slower forward stroke moves the material along to a new position.
Such conveyors have been used extensively in mining and industrial applications where they have been known as "shaker" or "flat stroke" conveyors. The trough reciprocates back and forth in the same plane and slides material along it as contrasted with vibrating or oscillating conveyors which toss material from position to position.
Typically, these conveyors have been driven by sophisticated and costly mechanical drive mechanisms. Although rugged and reliable, they have been limitedly adaptable to different operating conditions, incapable of conveying in more than one direction, and have a non-adjustable feed rate resulting from a stroke having a fixed amplitude and frequency. There has been little success in developing a simple, low maintenance fluid pressure drive for a large reciprocating conveyor which is readily adjustable for efficiently conveying a wide variety of materials under varied conditions of temperature, density, coefficient of function, moisture, etc.
Proposals have been made to drive reciprocating conveyors by hydraulic or pneumatic fluid pressure mechanisms for the purpose of design simplicity, reversibility, and adjustability of the feed rate. These have involved driving a reciprocably mounted conveyor trough by means of a cylinder, and controls therefor have varied from alternately applying air at different pressures to opposite sides of the cylinder such as shown in Campion U.S. Pat. No. 2,473,193, to unbelievably complex arrangements of hydraulic pumps, accumulators, and variable flow control valves such as shown in J. F. Joy U.S. Pat. No. 2,662,635.
Prior to this invention, none of these fluid pressure mechanisms have been satisfactory, especially for driving large industrial conveyors or feeders.
In the simple versions, fluid pressure was alternately supplied to opposite ends of a drive cylinder with little or no control over the acceleration rates during the forward and rearward strokes. The trough would not be reversed sharply enough at the terminal end of the forward stroke to move it backwardly with sufficient snap action to completely break the friction between the material and the trough, causing some of it to move rearwardly with the trough; and the trough would change direction too sharply at the terminal end of the rearward stroke, causing some of the material to shift rearwardly on the trough. And, uncontrolled or improper movement during the forward stroke would cause the trough to "slip" beneath the material, or not move rapidly enough during at least part of the forward stroke. In the complex versions, first cost has been prohibitive and maintenance costs and down time for repair have been unacceptable.
Another problem with reciprocating conveyors used as feeders for shredded vehicles or other scrap is frequent spark-generated dust explosions which distort or destroy the trough and blow shrapnel-like fragments about the surrounding area.
In view of the foregoing, there is a need for an economically priced, simple, reliable, adjustable-feed, low-maintenance fluid pressure drive mechanism for very large reciprocating troughs or pan feeders in the order of six or more feet wide with capacities of ten or more tons of steel scrap, coal, rock, ore and the like; and there is a need for harmlessly venting the gases produced in spark-generated dust explosions in the conveyor trough.